I think both Santorum and Dayton are basically 50/50. I also think both NE and RI are about 50/50. Beyond that, a lot could happen depending on who might retire.
Santorum's a lock, there is nobody in PA with enough clout or pull to take him out. He's popular, and the only thing really negative on him has been the kids schooling scandal which was basically a blip.
Santorum will win re-election easily.